Mechanics and Forces Quiz

A cream separator uses rapid rotation to create centrifugal force, which pushes the denser components of milk (skim milk) outward, allowing the lighter fat (cream) to collect near the center.

When the brush is in water, the hairs are separated by water. When removed, the surface tension of the water film between the hairs pulls them together to minimize the surface area.

Viscosity describes a fluid's internal resistance to flow and may be thought of as a measure of fluid friction. For example, high-viscosity folic magma will create a tall, steep strata volcano, because it cannot flow far before it cools, while low-viscosity manic lava will create a wide, shallow-sloped shield volcano. All real fluids (except super fluids) have some resistance to stress and therefore are viscous, but a fluid which has no resistance to shear stress is known as an ideal fluid or in viscid fluid.

Rutherford assumed that electrons are revolving around the nucleus in circular orbits of all possible redii. The necessary centripetal forces for circular motion of electrons around the nucleus is provided by electrostatic force of attraction between electrons and nucleus.
So 3^rd option is the correct answer.

Using the formula h = 1/2 * g * t^2, where g is approximately 32 ft/s^2 and t is 8 seconds: h = 0.5 * 32 * 64 = 16 * 64 = 1024 ft.

The centripetal force is calculated as F = (m * v^2) / r. Given m = 5 kg, v = 4 m/s, and r = 10 m: F = (5 * 16) / 10 = 80 / 10 = 8 N.

To get a resultant of 2 N from 14 N and 16 N, the forces must act in opposite directions. The angle between two vectors acting in opposite directions is 180 degrees.

Work done by the braking force equals the change in kinetic energy. Since both have the same initial kinetic energy and the same braking force, the work done to stop them (F * d) is equal, meaning the distance d must be the same.

In uniform circular motion, the velocity vector changes direction constantly. This change requires an acceleration directed toward the center of the circle, known as centripetal acceleration.

When the bottle is swung, the liquid is pushed outward by centrifugal force. The air bubbles, being less dense than the liquid, are displaced toward the region of lower pressure, which is the center of rotation (the neck).

Since force and displacement vector are perpendicular to each other when a body is moving in a circular path, so work done is 0 since we know that work done is the dot product of force applied and displacement of the particle.

Assertion A is false because velocity is a vector; in circular motion, the direction changes constantly, so velocity is not uniform. Reason R is true because the speed (magnitude of velocity) remains constant.

Path followed by a projectile is a parabolic path, so 2^nd option is the correct answer.

Assertion A is true because gravity decreases as you move further from the center of the Earth. Reason R is false because gravitational force decreases with height, not increases.

Assertion A is true because astronauts are in free fall. Reason R is true because objects in orbit are indeed experiencing centripetal force, but this force is not the cause of weightlessness; rather, the lack of a normal force is.

Warm air is less dense and rises, so ventilators near the ceiling allow it to escape. The reason is true, but it explains the assertion because warm air (which carries pollutants) rises to the top.

A car acts as a Faraday cage during a lightning strike. The charge stays on the outer surface of the metal body and conducts to the ground, protecting the occupants inside.

Translatory motion occurs when all points of a body move in the same direction with the same velocity. This can apply to any finite size body, regardless of its shape.

Gravitational force acting on a planet in circular motion is directed towards the center of the sun, while the instantaneous displacement vector is tangential to the orbit. Since work done is given by the dot product of force and displacement, and the angle between them is 90 degrees, the work done is zero.

We do not feel atmospheric pressure because the internal pressure of our body fluids and gases balances the external atmospheric pressure.

Sea water has a higher density than river water due to dissolved salts. According to Archimedes' principle, a denser fluid exerts a greater buoyant force (upward thrust) on an immersed object, making it easier to float or swim.

When a person runs, they must tilt their umbrella forward to counter their horizontal velocity relative to the falling rain. When they stop, their horizontal velocity becomes zero, so the rain falls straight down relative to them, meaning they must hold the umbrella vertically as before they started moving.